LETTER OF TRANSMITTAL. 



State Experiment Station. 



Dec. I. 1905. 

 His Excellency, John A. Johnson, St. Paul, Minn. 



Dear Sir: It gives me pleasure to present to you herewith the 

 tenth annual report from this department. 



This has been a year of surprises in that certain destructive 

 pests have been unexpectedly active, while -others which we will 

 always have with us and which usually work havoc each year have 

 done little or no injury during the past season. The Hessian Fly 

 has been present on grains and grasses, but to a limited extent, 

 not sufficiently noticeable to cause complaint. It is safe to say, 

 however, that this insect will be more noticeable the coming 

 season, and will, if climatic conditions favor, increase in numbers 

 each year for several seasons, until it reaches its climax in numbers 

 and injury done, after which it will practically disappear, as it has 

 this season, only to repeat the same phenomenon later. This peri- 

 odic increase and decrease in the numbers of this, probably our 

 most serious grain pest in Minnesota, is due largely to the presence 

 of parasitic insects which prey upon it. As the Hessian Fly in- 

 creases in numbers, so does its parasites, until the latter get the 

 upper hand, and the fly disappears. But in the killing of its host the 

 parasite has destroyed its food supply, and hence its numbers are 

 materially lessened, giving the Hessian Fly another chance. It is 

 estimated that the average annual loss in the United States alone, 

 due to this fly, amounts to nearly $50,000,000, and about five years 

 ago it raised that tax to $100,000,000 for one year, Ohio and Indiana 

 contributing $24,000,000 of that sum. The Chinch Bug, companion 

 pest of the Hessian Fly, has been conspicuous by its absence, 

 though a few were reported from one or two localities. This insect, 

 also while sparing us this year, will visit us again in destructive 



